Variable zig-zag resistor with tabs

ABSTRACT

A variable resistor of this invention includes tap electrodes, a sliding brush, zig-zag resistor having resistor films, and if necessary a wedge-shaped resistance layer connected series to the zig-zag resistor. The tap electrodes are spaced apart from each other and located in the path of the sliding brush, and the tap films of the tap electrodes are formed outside of said path. The resistor films of the zig-zag resistor are overlaid on the tap films. And the width of the tap films is made smaller than that of the resistor films but is made equal to the pattern spacing of the resistor films.

United States Patent Tsukamoto et al.

[ 1 July 4, 1972 [54] VARIABLE ZIG-ZAG RESISTOR WITH TABS [72] lnventorsz Masaaki Tsukamoto, Kawasaki; Tatsuo Fujii, Tokyo; Shigeo Ono, Yokohama, all

[21], Appl.No.: 95,146

[56] References Cited UNITED STATES PATENTS 2,354,808 8/1944 Ganci ..338/186 X 2/1971 Fujii ..338/l42 X 3,111,639 11/1963 Ploke ..338/140 3,431,640 3/1969 Larsson ..29/620 2,693,023 11/1954 Kerridge ...338/292 X 3,594,686 7/1971 Fujii ..338/140 Primary Examiner Lewis H. Myers Assistant ExaminerGerald P. Tolin Attorney-Ward, McElhannon, Brooks & Fitzpatrick 571 ABSTRACT A variable resistor of this invention includes tap electrodes, a sliding brush, zig-zag resistor having resistor films, and if necessary a wedge-shaped resistance layer connected series to the zig-zag resistor. The tap electrodes are spaced apart from each other and located in the path of the sliding brush, and the tap films of the tap electrodes are formed outside of said path. The resistor films of the zig-zag resistor are overlaid on the tap films. And 'the width of the tap films is made smaller than that of the resistor films but is made equal to the pattern spacing of the resistor films.

8 Claims, 4 Drawing Figures Patented July 4, 1972 2 Sheets-Sheet 1 FIG. I

PRIOR ART I loom 3' 3" Patnted July 4, 1972 2 Sheets-Sheet 2 FIG. 2

VARIABLE ZIG-ZAG RESISTOR WITH TABS BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a developed view of the prior art variable resistor;

FIG. 2 is a plan view of a variable resistor in accordance with the present invention;

FIG. 3 is a fragmentary view thereof on enlarged scale; and

FIG. 4 is a view similar to FIG. 3 but illustrating the abnormal condition.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable resistor and more specifically to the configurations of the resistance and electrode layers of a variable resistor of the type comprising a thin resistor film formed by deposition in vacuum, sputtering, etching, electro-forming or the like, a plurality of tap electrodes formed upon said resistance layers by the same process and a sliding brush for movement over said tap electrodes.

2. Description of the Prior Art FIG. 1 illustrates the prior art variable resistor disclosed in U.S. application Ser. No. 4987, filed on Jan. 22, 1970, now U.S. Pat No. 3594686, and West Germany application Ser. No. P 04 335.0, filed on Jan. 30, 1970 having the resistance film and electrodes both of which are formed by deposition in vacuum or sputtering through a mask. The resistance of this variable resistor varies in a continuous function manner. Tap electrodes 3,3 and 3" are formed at right angles relative to the path K of a wiper arm. A wedge-shaped resistance layer 1 width said tap film is made smaller than that of said resistance film, but is made equal to the spacing between said resistance films. Furthermore a wedge-shaped resistance layer is connected in series to said zig-zag resistor and tap electrodes which have tap films overlaid upon said wedge-shaped resistance layer are juxtaposed with respectto said tap electrodes for said zig-zag resistor DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 2, a brush makes contact with tap electrodes 7 and 7' of a conductive material ensuring a better electrical contact with the brush J and strong wear resistance. The

' tap electrodes 7 and 7' are deposited in vacuum so as to be has its width varied in accordance with a function. A step resistance section P comprises strip-shaped resistance layers 2 'which are formed outside of the path K and each of which is extended from each of the tap electrodes. A zig-zag resistance section Q comprises strip-shaped resistance layers 2' each pairs of which are extended from each of the tap electrodes 3. The strip-shaped resistance layers 2 and 2 in the step resistance section P and zig-zag resistance section Q', respectively, are interconnected with each other by connection taps 4 and 4. In the prior art variable resistor of the type described above, the tap electrodes 3 in the step resistance section P must have their lengths varied in accordance with the function while the connection taps 4 must have their positions varied in accordance with the function. Thus both of the taps 3' and 4 and the resistance layers 2 must be accurately formed. Since two resistance layers are formed for each tap in the zig-zag section Q, if the resistance layers and taps are not accurately formed, a'desired accuracy is not obtained. In the worst case, the resistance layers are not electrically connected to the taps, thus causing the disconnection in the resistor pattern.

SUMMARY OF THE INVENTION One of the objects of the present invention is to provide such a pattern that the range of a resistance value obtained from one resistance layer may be increased within a limited space at a right angle relative to the path of the wiper arm.

Another object of the present invention is to minimize the error in registration of an insulating base with a mask for fonning tap electrodes and the relative resistance errorcaused by the distortion of the pattern which in turn is caused by the thermal expansion of the base, mask and jigs.

A still another object of the present invention is to make smaller the spacing between the masking holes which greatly influence the accuracy. 4

A further object of the present invention is to provide a function type resistor with a higher degree of accuracy which may be manufactured in a simple manner at less cost with a least number of rejections and in which even though the resistor is of a tap type the width of the path of the wiper arm may be made small and the stable contact may be ensured for a long time.

In brief, the present invention provides a variable resistor in which tap electrodes for contact with a brush are spaced apart juxtaposed at equal spaces. A wedge-shaped resistance layer 5 has a relatively high surface resistivity and has its width 81 changed as with the prior art resistor so as to provide a resistor whose value changes in accordance with a function. The tap electrodes 7 and the wedge-shaped resistance layer 5 constitute the wedge-shaped resistance section P. A zig-zag pattern resistor 6 is deposited in vacuum simultaneously with the wedge-shaped resistance layer 5 in contiguous therewith and one branch of the zig-zag resistor 6 is provided for each tap electrode 7'. The tap electrodes 7' and the zig-zag resistor 6 constitute the zig-zag resistance section Q. The zig-zag resistor 6 is partially overlaid upon the tap electrodes 7 outside the path K of the brush J and as shown in FIG. 3 the width W of the tap portion B of the electrode 7 is made smaller than that W of the branch A of the zigzag resistor 6 while the spacing C between the branches A is made equal to the width W of the tap portion B.

An electrically insulating plate 8 upon which are deposited the above resistance layers is provided with a notch 8a which is located substantially at the center of the zig-zag resistance section Q and into which is fitted a pin 9 in the deposition process in order to eliminate the error in overlaying the zigzag resistor 6 over the tap electrodes 7. In other words, the notch 8a is a reference point for determining the positions of the wedge-shaped resistance layer 5 and the zigzag resistor 6 with respect to the tap electrodes 7 and 7 respectively. The brush J slides along the path K and the contacts J1 J5 of the brush .I are slantly arranged as shown in FIG. 2 so that contacts may make contact two or more than two taps. Reference character N designates a terminal electrode.

Next the mode of operation will be described. When a re- I sistor whose value is increased in a logarithmic manner is desired, the wedge-shaped resistance layer 5 must have its value increased gradually from terminal N in the circumferential direction. For this purpose, as the length of the wedge-shaped resistance layer 5 is increased, its width S1 is made smaller. However, from the standpoint of manufacture, the smallest width is limited. Since the resistance is in proportion to the length and in inverse proportion to the width, the zig-zag resistor in Q has a zig-zag pattern with the constant width S (See FIG. 3) so that within a limited space a resistance higher than that in the wedge-shaped resistance section P may be obtained. As shown in FIG. 3, the width W of the n'g-zag resistor 6 is made greater than the width W of the tap portion B of the tape electrode 7' while the spacing C between the branches A is made equal to the width W of the tap portion B. Therefore even when there occurs an error in overlaying the zig-zag resistor 6 over the tap electrodes 7, that is even when there occurs an error in the position of the tap portion B relative to the branch A (for example as shown in FIG. 4 at E), the tap portion B is formed upon the branch A when the error is less than one-half of a pitch D= W+ W. Even when the error is in excess of one-half of the tap pitch D, the tap electrode is made contact with the adjacent resistor branch because the from each other in the path of a brush or wiper arm; the tap spacing C between the branches A is made equal to the width W of the tap portion B. In other words, even when the error is in excess of one-half of the tap pitch D, it is equivalent to the case when the error is less than one-half of the tap pitch. The short-circuit or disconnection caused by the fact that the error is exactly one-half of the pitch D as shown at F in FIG. 4 is statistically very less. Thus a number of rejections due to the error may be greatly reduced.

In the manufacture of the prior art variable resistor as shown in FIG. I, a reference pin 11 is fitted into a notch 10a of the base 10 in case of deposition. The resistance layer 2, the tape electrodes 3, 3' and 3" and the connection taps 4 and 4 are deposited separately so that the errors in overlying or registration these films are inevitably produced. In consequence, the abnormal resistance is produced because of the nonuniform fiow of the current through the mis-aligned films or layers. Especially the low resistance portion is greatly affected. (The error becomes in excess of tolerance). According to the present invention, the zig-zag pattern resistance layer Q is formed as shown in FIG. 2 so that the connection taps 4 and 4' may be eliminated while only tap electrodes 7 and 7' are overlaid upon the resistance layers. Therefore the disconnection between the wedge-shaped resistance layer and the zigzag pattern resistance layer due to the error in overlaying will not occur. In addition, the abnormal resistance may be minimized. Since the patterns of the resistance layers are simple, the manufacture is simplified and the function type resistor having a stability over a wide range of resistance may be provided.

As described hereinabove, the value of the resistance which varies in accordance with a function will not be adversely affected even when the relative position of the tap electrode pattern with respect to the zig-zag resistance layer pattern is deviated about or in excess of one-half of the pitch. The resistance layers may be advantageously formed only by on deposition within a limited space and their relative errors are small while they have a wide range of resistance.

In addition the patterns for forming the tap electrodes and zig-zag resistance layer are simplified so that the masks may be used for many times and the tolerance in registration may be improved. Therefore, the tap electrodes and the zig-zag resistor may be obtained with a higher degree of accuracy and a less cost. The pitch of the tap electrode may be made smaller while the spacing between the taps may be also reduced so that the resistance may be continuously varied and detected with higher degree of accuracy. In addition, the width of the path of the brush or wiper arm may be made smaller and the stable contact may be ensured.

What is claimed is;:

l. A variable resistor comprising an insulating plate;

a movable brush;

a plurality of conductive tap electrodes formed side by side with equal spaces on said insulating plate,

said movable brush being arranged to traverse and engage said tap electrodes along a path, and each of said tap electrodes having at its one end a portion extending outside of said path;

a zig-zag resistance layer formed on said plate and outside said path,

the zig-zag resistance layer consisting of a plurality of first resistance strips formed side by side to each other and in parallel with saidtap electrodes, the number of said first resistance strips being twice the number of said tap electrodes,

a plurality of second resistance strips being made of the same material as that of said first resistance strips, said second resistance strips altemately'connecting upper and lower ends of neighboring first resistance strips so that said first and second resistance strips form the zigzag pattern,

said extending portions of said tap electrodes overlaying the second resistance strips which are arranged at the side adjacent the tap electrodes, respectively, each space between neighboring first resistance strips, of

which the lower ends are connected to each other, being equal to the width of each of said portions,

the length of each of said second resistance strips in the progressive direction of the zig-zag pattern being greater than the width of each of said portions. 7

2. A variable resistor according to claim 1, wherein said first resistance strips are progressively increased in length from one end to the other.

3. A variable resistor according to claim 1, wherein said first resistance strips are equal in width.

4. A variable resistor according to claim 1, further comprising a wedge-shaped resistance layer connected in series to said zig-zag resistance layer; and a plurality of second conductive tap electrodes juxtaposed at the same spacing as said tap electrodes for said zig-zag resistance layer,

each of said second tap electrodes having a portion superposed on said wedge-shaped resistance layer.

5. A variable resistor according to claim 1 wherein said path is arcuately shaped.

6. In a variable resistor, a plurality of tap electrodes formed side by side in spaced relationship on an insulating plate, each of said tap electrodes having an extending portion, a zig-zag resistance layer formed on said plate adjacent said extending portions, said zig-zag resistance layer comprising a plurality of first resistance strips formed in side-by-side relationship and in substantially parallel relationship with respect to said extending portions, the number of first resistance strips being twice the number of said extending portions, a plurality of second resistance strips alternately connecting upper and lower ends of neighboring first resistance strips so that said first and second resistance strips form a zig-zag pattern, said extending portions of said electrodes overlaying the second resistance strips which are arranged at the side adjacent the tap electrodes respectively, the length of each of said second resistance strips in the progressive direction of the zigzag pattern being greater than the Width of each of said extending portions.

7. Apparatus according to claim 6 wherein each space between neighboring first resistance strips is equal to the width of each of said extending portions.

8. Apparatus according to claim 6 wherein the width of each of said first resistance strips are substantially equal. 

1. A variable resistor comprising an insulating plate; a movable brush; a plurality of conductive tap electrodes formed side by side with equal spaces on said insulating plate, said movable brush being arranged to traverse and engage said tap electrodes along a path, and each of said tap electrodes having at its one end a portion extending outside of said path; a zig-zag resistance layer formed on said plate and outside said path, the zig-zag resistance layer consisting of a plurality of first resistance strips formed side by side to each other and in parallel with said tap electrodes, the number of said first resistance strips being twice the number of said tap electrodes, a plurality of second resistance strips being made of the same material as that of said first resistance strips, said second resistance strips alternately connecting upper and lower ends of neighboring first resistance strips so that said first and second resistance strips form the zig-zag pattern, said extending portions of said tap electrodes overlaying the second resistance strips which are arranged at the side adjacent the tap electrodes, respectively, each space between neighboring first resistance strips, of which the lower ends are connected to each other, being equal to the width of each of said portions, the length of each of said second resistance strips in the progressive direction of the zig-zag pattern being greater than the width of each of said portions.
 2. A variable resistor according to claim 1, wherein said first resistance strips are progressively increased in length from one end to the other.
 3. A variable resistor according to claim 1, wherein said first resistance strips are equal in width.
 4. A variable resistor according to claim 1, further comprising a wedge-shaped resistance layer connected in series to said zig-zag resistance layer; and a plurality of second conductive tap electrodes juxtaposed at the same spacing as said tap electrodes for said zig-zag resistance layer, each of said second tap electrodes having a portion superposed on said wedge-shaped resistance layer.
 5. A variable resistor according to claim 1 wherein said path is arcuately shaped.
 6. In a variable resistor, a plurality of tap electrodes formed side by side in spaced relationship on an insulating plate, each of said tap electrodes having an extending portion, a zig-zag resistance layer formed on said plate adjacent said extending portions, said zig-zag resistance layer comprising a plurality of first resistance strips formed in side-by-side relationship and in substantially parallel relationship with respect to said extending portions, the number of first resistance strips being twice the number of said extending portions, a plurality of second resistance strips alternately connecting upper and lower ends of neighboring first resistance strips so tHat said first and second resistance strips form a zig-zag pattern, said extending portions of said electrodes overlaying the second resistance strips which are arranged at the side adjacent the tap electrodes respectively, the length of each of said second resistance strips in the progressive direction of the zig-zag pattern being greater than the width of each of said extending portions.
 7. Apparatus according to claim 6 wherein each space between neighboring first resistance strips is equal to the width of each of said extending portions.
 8. Apparatus according to claim 6 wherein the width of each of said first resistance strips are substantially equal. 